Many factors influence the quality of a romantic relationship, and there has been increasing evidence that early attachment plays a vital role in adult bonds, including romantic relationships. However, most of the literature has focused on the role of parent–child and peer attachments with little focus on sibling attachments. Using the Sibling Relationship Questionnaire, we asked a sample of New Zealand university students to retrospectively rate the relationship they had with a significant sibling during their adolescence, and to rate their current romantic relationship quality using the Relationship Assessment Scale. We found no significant correlations between the subscales of the Sibling Relationship Questionnaire and the Relationship Assessment Scale. However, further analysis uncovered a significant association between the Relationship Assessment Scale, birth order, and relationship length.